Bypass of GRUB lockdown restriction in Secure Boot mode via serial command MMIO base address

Description

A local attacker with control over GRUB's configuration can bypass lockdown restrictions when booting with Secure Boot and load an unsigned GRUB module, while GRUB continues to report lockdown is enabled. The vulnerability is caused by insufficient validation of the MMIO base address passed to the GRUB serial command. GRUB does not validate that the base address corresponds to a UART device, rather than being an arbitrary memory address. This allows an attacker to trick GRUB into writing non-arbitrary data at an attacker-controlled address, including resetting the grub_file_verifiers list in a way that disables the subsequent verification of loaded modules.

Scores

EPSS (exploitation in 30 days)

0.11% · top 98% of all CVEs (6 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: total

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.4.

Weakness

• CWE-822 Untrusted pointer dereference (opens in a new tab)All about CWE-822 and its CVEs

Affected products

• GNU · grub2

  • affected 2.12 – < 2.16

References (2)

• https://www.openwall.com/lists/oss-security/2026/09/13/5 (opens in a new tab)mailing-list
• https://gitlab.freedesktop.org/gnu-grub/grub/-/commit/26beaa3b2720fefdc4d04c1ae209b776fe6848d6 (opens in a new tab)patch

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-97876](https://trackcve.app/badge/CVE-2026-97876.svg)](https://trackcve.app/cve/CVE-2026-97876)

Record last updated 2 Oct 2026, 17:45 UTC.